The invention relates to a boring tool for a bone, particularly the proximal femur. More particularly, the invention relates to a tool for forming a bore in the head of the femur for receiving a femoral neck screw.
It is known to use femoral neck pins, particularly femoral neck screws, for the repair of femoral fractures, particularly that of the proximal femur. They are introduced in combination with either a so-called Pohl butt or side plate or a locking nail. In the former case, a butt plate or side plate which is extramedullarily fixed to the bone for example to the outer bone surface, contains a sleeve through which the femoral neck screw is passed. When a locking nail is used, in the latter case, the locking nail has an oblique bore for receiving the femoral neck screw.
To securely anchor the femoral neck screw in the bone, the bone is commonly bored open up to the core thread diameter before the femoral neck screw is threaded in.
Before such a boring procedure is performed, it is necessary first to determine the boring axis and, thus, the position of the femoral neck screw in the bone by X-ray control. This is commonly accomplished with a Kirschner threaded wire. After the correct position is determined the Kirschner threaded wire will be left in the bone and serves as a guide for the boring tool and also subsequently in threading the femoral neck screw. For this reason, both the boring tool and femoral neck screw are provided with an axial through bore, i.e. cannulation.
The boring tool, such as a drill or reamer, has a suitable boring portion at the front end of its elongate shank and a portion at the rear end for connection to a rotary drive tool such as a power drill. The tool can be made in two pieces with a locking portion on one of the pieces to operatively connect the front and rear portions.
Under certain conditions, the comparatively thin Kirschner threaded wire can buckle or warp while being introduced in the femoral neck. Therefore, it is indispensable to monitor the position of the Kirschner threaded wire by X-ray control. This prevents the wire from being unintentionally advanced into the hip joint as the warped portion gets stuck in the bore of the boring tool or femoral neck screw. Consequently, warping or buckling of the wire must be avoided.